What This Ampere kW Calculator Does
This ampere kW calculator helps you convert electrical current (amps) to power (kilowatts), and power back to current. It supports single-phase AC, three-phase AC, and DC systems. That makes it useful for electricians, engineers, solar installers, facility managers, and anyone sizing circuits, breakers, generators, or loads.
If you are asking questions like “How many kW is 20 amps?” or “How many amps does a 7.5 kW motor draw?”, this calculator gives fast answers with the correct formula for your system type.
How to Use the Calculator
- Select Amps to kW or kW to Amps.
- Choose system type: AC single phase, AC three phase, or DC.
- Enter the voltage.
- Enter either amps or kW based on your conversion type.
- For AC, enter a realistic power factor (typically 0.8 to 1.0).
- Click Calculate to get your result and formula breakdown.
Amps to kW Formula
1) Single-Phase AC
kW = (V × A × PF) ÷ 1000
Where V is voltage, A is current in amps, and PF is power factor.
2) Three-Phase AC
kW = (√3 × V × A × PF) ÷ 1000
Three-phase systems include the √3 (1.732) multiplier when using line-to-line voltage.
3) DC
kW = (V × A) ÷ 1000
DC has no power factor in the same sense as AC load calculations, so PF is not used.
kW to Amps Formula
1) Single-Phase AC
A = (kW × 1000) ÷ (V × PF)
2) Three-Phase AC
A = (kW × 1000) ÷ (√3 × V × PF)
3) DC
A = (kW × 1000) ÷ V
Worked Examples
Example A: 240V Single-Phase, 25A, PF 0.95
kW = (240 × 25 × 0.95) ÷ 1000 = 5.70 kW
Example B: 400V Three-Phase, 30A, PF 0.9
kW = (1.732 × 400 × 30 × 0.9) ÷ 1000 = 18.71 kW
Example C: 5 kW Single-Phase at 230V, PF 0.9
A = (5 × 1000) ÷ (230 × 0.9) = 24.15 A
Common Mistakes to Avoid
- Using single-phase formula for three-phase equipment.
- Forgetting power factor in AC calculations.
- Entering line-to-neutral voltage when line-to-line is required (or vice versa).
- Assuming nameplate kW equals real-time operating load in all conditions.
- Ignoring startup current for motors and compressors.
Quick Notes on Voltage and Power Factor
Typical voltages vary by country and application: 120V, 208V, 230V, 240V, 400V, 415V, and 480V are common. Power factor for resistive heating loads may be near 1.0, while motors and inductive equipment can be lower. If you do not know PF, check equipment data plates or manuals.
FAQ
Is kW the same as kVA?
No. kW is real power, while kVA is apparent power. They are related by power factor: kW = kVA × PF.
Can I use this for generator sizing?
Yes for basic estimates, but include surge current, diversity factors, and local code requirements for final sizing.
What if I have milliamps?
Convert first: 1000 mA = 1 A. Then use the calculator.
Final Takeaway
A reliable amps-to-kW and kW-to-amps conversion is essential for safe and efficient electrical design. Use the correct phase formula, enter a realistic power factor for AC loads, and verify with equipment specifications. This tool gives quick, practical answers for day-to-day electrical planning.